It is estimated that the prevalance of epilepsy is between 3 and 6 persons per 1000 individuals. for most persons afflicted with epilepsy, pharmacotherapy is the primary form of treatment; antiepileptic drugs also occasionally are used in an attempt to improve the behavior of mentally ill or mentally retarded individuals. Although the physiological side effects of antiepileptic agents are widely acknowledged as problematic, little attention has been paid to possible behavioral side effects of such drugs. Clinical investigations have yielded conflicting results, and preclinical studies have begun to appear only recently. The proposed studies represent an initial attempt to determine the preclinical behavioral pharmacology of primidone, methsuximide, and mephenytoin, and to extend prior findings concerning the preclinical behavioral pharmacology of phenytoin, valproic acid, phenobarbital; clonazepam, and ethosuximide. Each of these drugs is used in the clinical management of epilepsy. The effects of antiepileptic drugs will be examined, using pigeons as subjects, under 1) a multiple fixed-ratio fixed-interval schedule of food delivery, 2) a repeated acquisition procedure, 3) a delayed-matching-to-sample procedure, 4) an automaintenance procedure, 5) a negative automaintenance procedure, 6) a fixed-consecutive-number schedule (with and without external discriminative stimulti, and 7) a two-key drug discrimination procedure. Obtained results combined with the findings of prior investigations are expected to provide a profile of each drug's behavioral actions (e.g., its effects on learning, memory, and punished behavior, and its sensory consequences). Obtained results may by implication be of clinical significance, and should at minimum aid clinical researchers by suggesting the kinds of deleterious behavioral side effects likely to be produced by a particular medication.